Jump to content

Archived

This topic is now archived and is closed to further replies.

Kelly

Science discussion, continued from other thread

Recommended Posts

Kelly

Sarafine and P describe a spoof of the Born–Oppenheimer approximation:

0000039789_20070516162711.jpg

Share this post


Link to post
Share on other sites
daveb

Sarafine and P describe a spoof of the Born–Oppenheimer approximation:

0000039789_20070516162711.jpg

There's a big bang in the P and Serafine thread! (it is "er", right?)

Share this post


Link to post
Share on other sites
A Long Time Ago

Sarafine and P describe a spoof of the Born–Oppenheimer approximation:

0000039789_20070516162711.jpg

There's a big bang in the P and Serafine thread! (it is "er", right?)

:lol: :lol: :lol: :lol: :lol:

Now to be a bit more serious.

The sad part is that I am pretty sure the stuff on the white board is gibberish (though gibberish written the right way in the right physics language to look very plausible) but I could be wrong and it could be something they just grabbed out of a real paper (I am not a particle physicist so that really isn't my area of expertise but I am pretty sure that the Born-Oppenheimer approximation is something else if I remember correctly from my Quantum II class last year).

Share this post


Link to post
Share on other sites
daveb

My understanding is they have real physicists help them out with things like the stuff on the whiteboards, as well as "science" jokes and such. But to be honest I have no clue if any of the stuff on that whiteboard really means anything. (Kelly might know, though)

Share this post


Link to post
Share on other sites
A Long Time Ago

My understanding is they have real physicists help them out with things like the stuff on the whiteboards, as well as "science" jokes and such. But to be honest I have no clue if any of the stuff on that whiteboard really means anything. (Kelly might know, though)

You are right that Kelly would probably know. Do we have any other physics people here on AVEN besides Kelly and I?

The one thing I can say is that physicists do not write it out that neat on whiteboards or chalkboards. I do quite a bit better than average and I make a real mess.

Share this post


Link to post
Share on other sites
michaeld

My understanding is they have real physicists help them out with things like the stuff on the whiteboards, as well as "science" jokes and such. But to be honest I have no clue if any of the stuff on that whiteboard really means anything. (Kelly might know, though)

You are right that Kelly would probably know. Do we have any other physics people here on AVEN besides Kelly and I?

The one thing I can say is that physicists do not write it out that neat on whiteboards or chalkboards. I do quite a bit better than average and I make a real mess.

I'm not a physicist but I have enough background to understand that. It's nothing to do with the Born-Oppenheimer approximation. It's flavour-changing weak decay of quarks. The first equation gives the probability of a top quark decaying into a bottom quark. Here V_tb, V_td, V_ts are 3 elements of the well known CKM matrix, which incidentally also appears, in part, at the bottom of the board (parametrized in terms of sines and cosines of the Euler angles and the CP-violating phase).

The Feynman diagram at the top illustrates this reaction, whereas the other two Feynman diagrams are for the decay to charmed and up quarks (showing photon and W,Z boson exchange).

Share this post


Link to post
Share on other sites
daveb

The one thing I can say is that physicists do not write it out that neat on whiteboards or chalkboards. I do quite a bit better than average and I make a real mess.

:lol:

(I did recognize that some of the things on there were Feynman diagrams, but that's about all I could tell you - it's all over my head.)

Share this post


Link to post
Share on other sites
A Long Time Ago

My understanding is they have real physicists help them out with things like the stuff on the whiteboards, as well as "science" jokes and such. But to be honest I have no clue if any of the stuff on that whiteboard really means anything. (Kelly might know, though)

You are right that Kelly would probably know. Do we have any other physics people here on AVEN besides Kelly and I?

The one thing I can say is that physicists do not write it out that neat on whiteboards or chalkboards. I do quite a bit better than average and I make a real mess.

I'm not a physicist but I have enough background to understand that. It's nothing to do with the Born-Oppenheimer approximation. It's flavour-changing weak decay of quarks. The first equation gives the probability of a top quark decaying into a bottom quark. Here V_tb, V_td, V_ts are 3 elements of the well known CKM matrix, which incidentally also appears, in part, at the bottom of the board (parametrized in terms of sines and cosines of the Euler angles and the CP-violating phase).

The Feynman diagram at the top illustrates this reaction, whereas the other two Feynman diagrams are for the decay to charmed and up quarks (showing photon and W,Z boson exchange).

Thank you. Now that I know how quarks are labelled, it is making a bit more sense, though it is still not something I am familiar with other than Euler Angles (I am a classical physicist, what can I say).

Reminds me of the story of how the quarks got their names.

The first two to be "discovered" were the up and down (they are kind of like each other's partners) at the same time. Why they chose these directions I do not know (though it is probably out there somewhere). Then they found another quark but couldn't find its partner, so they called it the strange quark since they thought there should be another quark. Then later with more powerful accelerators, they found its partner, and now everything worked like a charm, hence it was called the charm quark. Now with the top and bottom quarks, they decided to do an opposites theme like up and down and chose this one so that their antiparticles could be called topless and bottomless.

Share this post


Link to post
Share on other sites
michaeld

Thank you. Now that I know how quarks are labelled, it is making a bit more sense, though it is still not something I am familiar with other than Euler Angles (I am a classical physicist, what can I say).

But quantum physics is where all the fuuuuuun happens. :D

Share this post


Link to post
Share on other sites
A Long Time Ago

Thank you. Now that I know how quarks are labelled, it is making a bit more sense, though it is still not something I am familiar with other than Euler Angles (I am a classical physicist, what can I say).

But quantum physics is where all the fuuuuuun happens. :D

But all the quantum people (spare a few) overlook the fun of turbulence and the incredible difficulty of fluid mechanics (we have been working on it for many centuries and will have many many more centuries of work to do in it).

Share this post


Link to post
Share on other sites
michaeld

Thank you. Now that I know how quarks are labelled, it is making a bit more sense, though it is still not something I am familiar with other than Euler Angles (I am a classical physicist, what can I say).

But quantum physics is where all the fuuuuuun happens. :D

But all the quantum people (spare a few) overlook the fun of turbulence and the incredible difficulty of fluid mechanics (we have been working on it for many centuries and will have many many more centuries of work to do in it).

True; in fact you can even earn a million dollars by solving the Navier-Stokes problem, which is generally regarded as a possible first step towards understanding turbulence.

There certainly is such a thing as quantum fluid dynamics though! A previous uni I was at had a well known research group; some of my friends were studying this (though more were doing classical fluids). I don't know a great deal about quantum fluids though.

Share this post


Link to post
Share on other sites
A Long Time Ago

Thank you. Now that I know how quarks are labelled, it is making a bit more sense, though it is still not something I am familiar with other than Euler Angles (I am a classical physicist, what can I say).

But quantum physics is where all the fuuuuuun happens. :D

But all the quantum people (spare a few) overlook the fun of turbulence and the incredible difficulty of fluid mechanics (we have been working on it for many centuries and will have many many more centuries of work to do in it).

True; in fact you can even earn a million dollars by solving the Navier-Stokes problem, which is generally regarded as a possible first step towards understanding turbulence.

There certainly is such a thing as quantum fluid dynamics though! A previous uni I was at had a well known research group; some of my friends were studying this (though more were doing classical fluids). I don't know a great deal about quantum fluids though.

The quantum fluid dynamics thing is why I said "spare a few" (bolded up above).

The Navier-Stokes problem has been standing for over 150 years and the most anyone can do is get is analytical statistical predictions from it and numerical deterministic predictions with the help of computers. I doubt humans are intelligent enough to analytically solve the Navier-Stokes equation.

Share this post


Link to post
Share on other sites
michaeld

The Navier-Stokes problem has been standing for over 150 years and the most anyone can do is get is analytical statistical predictions from it and numerical deterministic predictions with the help of computers. I doubt humans are intelligent enough to analytically solve the Navier-Stokes equation.

Well you don't need to solve the equation analytically to win the $1,000,000; you only need to prove the existence of smooth global solutions in 3 dimensions.

Share this post


Link to post
Share on other sites
Kelly
It's nothing to do with the Born-Oppenheimer approximation.

:)

In the show, Sheldon points to the part below the Feynman diagrams and says, That down there, it's just a joke. It's a spoof of the Born-Oppenheimer Approximation.

And I thought, I don't get it. :unsure:

Perhaps I am not the only one. :cake:

*noms petits fours*

Share this post


Link to post
Share on other sites
michaeld
It's nothing to do with the Born-Oppenheimer approximation.

:)

In the show, Sheldon points to the part below the Feynman diagrams and says, That down there, it's just a joke. It's a spoof of the Born-Oppenheimer Approximation.

And I thought, I don't get it. :unsure:

So he was pointing at the CKM matrix (in blue)? (Actually the thing in blue is only the first column of the CKM matrix; the second and third are replaced by ellipses.)

Yeah I still don't see any connection between the Born-Oppenheimer approximation and the CKM matrix - or anything else on the board for that matter.

Share this post


Link to post
Share on other sites
Kelly
So he was pointing at the CKM matrix (in blue)? (Actually the thing in blue is only the first column of the CKM matrix; the second and third are replaced by ellipses.)

Yeah I still don't see any connection between the Born-Oppenheimer approximation and the CKM matrix - or anything else on the board for that matter.

Yes. And specifically, the -S12C23 term. But that term is correct. Below is the matrix equation with the missing terms:

CKM.jpg

So, I fail to see the joke.

BTW (for the curious), a simple way of writing the Born-Oppenheimer approximation is:

3c63846f74575e899e96c5b77dcc22aa.png

Things can get complicated, though, and can break down. Anyway...

Share this post


Link to post
Share on other sites
michaeld

BTW (for the curious), a simple way of writing the Born-Oppenheimer approximation is:

3c63846f74575e899e96c5b77dcc22aa.png

Things can get complicated, though, and can break down. Anyway...

Heh. If the Born-Oppenheimer approximation is complicated think how much worse things are when you don't make this approximation. Even helium, the second lightest atom, becomes analytically intractable!

Share this post


Link to post
Share on other sites
Kelly
Heh. If the Born-Oppenheimer approximation is complicated think how much worse things are when you don't make this approximation.

So, maybe that itself is the joke.

From what I see, he is discussing the tecay of the top quark. He works out the decay ratio of the top quark to a W boson (T -> Wb). The calculations are shown, and in the paper:

http://pdg.ihep.su/1999/kmmixrpp.pdf

We see that it is about 100%:

decay.jpg

BTW, the article Top Properties and Rare Decays from the Tevatron (from Hadron Collider Physics 2005) discussed finding the upper and lower limits experimentally of B(t -> Wb)/B(t -> Wq) and suggested that it should be nearly 100%.

Anyway, Sheldone calculates this to be 99.82%, which is not a surprise so far.

Next, he shows Feynman Diagrams. Here is a typical one involving the tau lepton:

20090514210426!Tau-decay.png

And then he goes to flavor-changing neutral current Feynman diagrams (but F.C.N.C...).

Here is an example of such (again using the tau):

20060212024452!Tau-decay-fcnc.png

Below are some top quark decay diagrams. we see that his first Feynman diagram is like these, but simplified:

tdecay.jpgfeynman_t_lnuqq_yellowbg.gif

Lastly, he shows the CKM matrix partially written out, and calls that the joke. Perhaps those working with atoms, the need to slog through difficult equations (resorting to the Born-Oppenheimer Approximation) seems funny, because he can use the simpler CKM Matrix when working on quarks. Ha ha, suckers! :twisted: :P

Perhaps other physicists will explain all of this better (I am quite rusty).

:cake:

Share this post


Link to post
Share on other sites
Herr Joseph von Löthing

Can we do some real physics?

Y'know, macro scale stuff?

Share this post


Link to post
Share on other sites
A Long Time Ago

Can we do some real physics?

Y'know, macro scale stuff?

You do know that particle physics can be macro stuff. Very high energy cosmic rays (often they are protons or other nuclei) can hit earth's atmosphere with as much energy as 1 to 10 Joules (equivalent to the kinetic energy of a thrown shoe).

Share this post


Link to post
Share on other sites
Herr Joseph von Löthing

Can we do some real physics?

Y'know, macro scale stuff?

You do know that particle physics can be macro stuff. Very high energy cosmic rays (often they are protons or other nuclei) can hit earth's atmosphere with as much energy as 1 to 10 Joules (equivalent to the kinetic energy of a thrown shoe).

Ooohh.

Not as fun as mechanics, though.

Share this post


Link to post
Share on other sites
Kelly
Not as fun as mechanics, though.

Joseph can solve the Three Body Problem. :cake:

Share this post


Link to post
Share on other sites
A Long Time Ago

Solve the three body problem and I think you would get the nobel prize.

Share this post


Link to post
Share on other sites
Bobandirus

Eat this physicists :P

Metabolism_790px_partly_labeled.png

Share this post


Link to post
Share on other sites
Kelly

What are the enzymes responsible for each conversion?

Just kidding :P (but you just might know all of them)

:cake: to biochemists

Share this post


Link to post
Share on other sites
Bobandirus

I dont know many of them at all! Im only a first year :lol:. Even our biochem lecturer said he'd have to look up the details of the standard metabolic pathway, as theses no point in learning it. Its one of the best documented paths m theses on point in even testing to any great detail. Which is a releafe for me :lol: Im not fond of biochem. Behaviourial biology is so much more interesting.

Edit: that picture is perfect :P

Share this post


Link to post
Share on other sites
A Long Time Ago

Eat this physicists :P

Metabolism_790px_partly_labeled.png

I recognized this right away as glycolisis and the Kreb's cycle along with how things other than glucose enter into the pathway. I really loved biology. My favorite enzyme is rubisco (part of fixing carbon in photosynthesis) because it is one of the most inefficient proteins there is (in a typical plant, half the protein is rubisco just to get enough for the plant to live). Go biology! And for that matter, go chemistry! (now all the other physicist stare at me like I am from another planet)

Share this post


Link to post
Share on other sites
michaeld
Heh. If the Born-Oppenheimer approximation is complicated think how much worse things are when you don't make this approximation.

So, maybe that itself is the joke.

From what I see, he is discussing the tecay of the top quark. He works out the decay ratio of the top quark to a W boson (T -> Wb). The calculations are shown, and in the paper:

Well the top quark to a W boson + a bottom quark actually. Note the North-East leg of the Feynman diagram. (Also, of course, the bottom quark is needed to conserve baryon number - and charge for that matter.)

Lastly, he shows the CKM matrix partially written out, and calls that the joke. Perhaps those working with atoms, the need to slog through difficult equations (resorting to the Born-Oppenheimer Approximation) seems funny, because he can use the simpler CKM Matrix when working on quarks. Ha ha, suckers! :twisted: :P

Could well be. I've simply never "got" maths/physics humour. Perhaps because it all seems a little too natural that it's no longer funny.

Oh and Joe, you can't get more real than microscopic physics. In fact, microscopic physics is the key to understanding the macroscopic world at a deep level.

Share this post


Link to post
Share on other sites
Kelly
Well the top quark to a W boson + a bottom quark actually. Note the North-East leg of the Feynman diagram. (Also, of course, the bottom quark is needed to conserve baryon number - and charge for that matter.)

Oh, yes, I know. I had the bottom quark in my original sentence, but when it all got assembled and posted, that part seems to have disappeared. :redface:

Yes, we see that in the diagram.

*goes back into hiding*

*and still does not get the joke about the BO Approximation paraody* :unsure:

Here is another way of looking at that diagram, but also rotating it to see the creation of a top quark:

singletopAnimationst3.gif

Share this post


Link to post
Share on other sites
A Long Time Ago

Oh and Joe, you can't get more real than microscopic physics. In fact, microscopic physics is the key to understanding the macroscopic world at a deep level.

Yep, if you understand it at the microscopic level, you can in principle work your way up. As this is often easier said than done, a lot of our understanding of the macroscopic world first has to be empirical while waiting for the bottom up understanding to follow later.

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.

×
×
  • Create New...